Ship bottoms, underwater structures, fishing nets and the like are likely to have their appearance and function damaged by the adhesion to surface and propagation of various aquatic organisms including animals such as shellfishes, hard-shelled mussels and barnacles, plants such as laver (seaweeds) and bacteria which is caused when they are exposed to water for a prolonged period of time.
In particular, when such an aquatic organism adheres to a ship's bottom and propagates, it may occur that the surface roughness of the ship as a whole is increased to thereby lower the speed of the ship and increase the fuel consumed by the ship. Removing the aquatic organism from the ship bottom necessitates spending of extensive labor and working time. Also, when bacteria adhere to, for example, an underwater structure and propagate and, further, slime (sludgy matter) adheres thereto to cause putrefaction, or when a large sticky organism adheres to the surface of an underwater structure, for example, steel structure and propagates to thereby damage the coating for corrosion prevention provided on the underwater structure, there is the danger that damages such as deterioration of the strength and function of the underwater structure and thus marked shortening of the life thereof are invited.
It is common practice to apply, for example, a composition comprising a copolymer of tributyltin methacrylate and methyl methacrylate or the like and cuprous oxide (Cu2O) as an antifouling paint having excellent antifouling properties to ship bottoms, etc. so as to avoid the above damages. This copolymer of the antifouling paint is hydrolyzed in the seawater to thereby liberate organotin compounds such as bistributyltin oxide (tributyltin ether of the formula Bu3Sn—O—SnBu3 wherein Bu is a butyl group) and tributyltin halides (Bu3SnX wherein X is a halogen atom), so that an antifouling effect is exerted. Furthermore, the copolymer hydrolyzate per se is a “hydrolyzable self-polishing paint” which is rendered water-soluble and thus is dissolved in the seawater, so that no resin residue is left on the surface of the ship bottom coating with the result that always an active surface can be maintained.
However, the above organotin compounds are so highly toxic that apprehensions are being entertained with respect to marine pollution, occurrence of anomalous fish and anomalous shellfish and adverse effects on ecosystem through food chain. Therefore, the development of a nonstannic antifouling paint is desired as a substitute therefor.
For example, antifouling paints based on silyl esters as described in Japanese Patent Laid-open Publication Nos. 4(1992)-264170 (reference (a)), 4(1992)-264169 (reference (b)) and 4(1992)-264168 (reference (c)) can be mentioned as the above nonstannic antifouling paint. However, these antifouling paints have such problems that not only are their antifouling capabilities poor but also cracking and peeling are likely to occur as pointed out in Japanese Patent Laid-open Publication Nos. 6(1994)-157941 (reference (d)) and 6(1994)-157940 (reference (e)).
Further, Japanese Patent Laid-open Publication No. 2(1990)-196869 (reference (f)) teaches, for example, an antifouling paint comprising a blocked acid-functionality copolymer (A) which is obtained by copolymerizing trimethylsilyl methacrylate, ethyl methacrylate and methoxyethyl acrylate in the presence of an azo polymerization initiator and which contains a triorganosilyl carboxylate ester group, namely, a carboxylic acid group blocked with a trimethylsilyl group; a polycationic compound (B) which is an organic-solvent-soluble salt of polyvalent metal; and a biocide. In the use of this antifouling paint, for example, the trimethylsilyl group blocking the carboxylic acid group is split off by water contained in the paint, and the polyvalent cation reacts with thus formed carboxylic acid group of the acid-functionality copolymer (A), thereby effecting a crosslinking and hardening. However, in this reference, there is no description with respect to a method of coping with water produced by, for example, adding a carboxylic acid and zinc white (zinc oxide) to the paint. Further, the antifouling paint poses such a problem that when a free acid remains in the antifouling paint, the antifouling paint loaded with a component which reacts with a free acid to thereby produce water, there occur, for example, gelation and thickening causing deterioration of storage stability, deterioration of performance, etc. Still further, there is such a problem that when the acid-functionality copolymer (A) is hydrolyzed and when a crosslinking reaction occurs between thus formed acid group and the polycation, the elution (leaching) of the acid-functionality copolymer (A) would be suppressed to result in deterioration of the abradability of coating film and deterioration of long-term antifouling capability.
Thus, the antifouling paint described in the above reference has poor storage stability, and the coating film obtained from the antifouling paint has a drawback in that the cracking resistance thereof is not fully satisfactory.
Published Japanese Translation of PCT Patent Applications from Other States, No. 60(1985)-500452 (reference (g)) and Japanese Patent Laid-open Publication No. 63(1988)-215780 describe a resin for antifouling paint which is obtained by copolymerizing a vinyl monomer having an organosilyl group, such as a trialkylsilyl ester of (meth)acrylic acid, with another vinyl monomer and which has a number average molecular weight of 3000 to 40,000. It is further described that the resin can be blended with an organic water coupler such as trimethyl orthoformate, an antifouling agent such as cuprous oxide and a pigment such as red iron oxide. However, as described in the above Japanese Patent Laid-open Publication No. 6(1994)-157940 (reference (e)), this resin for antifouling paint has drawbacks in that it is likely to gel during the storage thereof and that the coating film formed from the antifouling paint is poor in cracking and peeling resistances.
Japanese Patent Publication No. 5(1993)-32433 corresponding to the above Published Japanese Translation of PCT Patent Applications from Other States, No. 60(1985)-500452 (reference (g)) discloses an antifouling paint comprising a poison (a) and a polymer binder (b) having a repeating unit of the formula —CH2—CX(COOR)—(B)— (wherein X is H or CH3, R is SiR′3 or Si(OR′)3 in which R′ is an alkyl group, etc. and B is an ethylenically unsaturated monomer residue), which polymer binder has a specified hydrolysis rate. Further, it is described that the antifouling paint can contain a solvent, a water-sensitive pigment component, an inert pigment, a filler and a retarder. However, the coating film obtained from the antifouling paint described in this reference has a drawback in that its cracking resistance is poor.
Japanese Patent Laid-open Publication No. 3(1991)-31372 (having matured to Japanese Patent No. 2775862, reference (h)) discloses a coating composition for preventing the attachment of organisms, comprising a polymer of monomer A and/or a copolymer AB from the monomer A and a vinyl polymerizable monomer B which is copolymerizable with the monomer A, an antifouling agent and a surfactant. The monomer A is represented by the formula CH2═C(X)—C—(═O)—OR (I) (wherein X is H or —CH3, and R is an organic group represented by the formula: 
wherein n is 0 or 1; m is a real number of 0 or greater; each of R1 to R3 represents a group such as an alkyl, an alkoxyl or phenyl; and each of R4 and R5 represents the same group as represented by R1 to R3 or a group selected from organosiloxane groups of the formula: 
wherein each of R6 to R8 represents the same group as represented by R1 to R3 or a group of the formula (b),
provided that m groups represented by R4 and R5 may be identical with or different from each other). As the surfactant, there are mentioned, for example, a fatty acid of −5° C. or higher melting point having 8 or more carbon atoms and an ester thereof. It is described that because the polymer A and copolymer AB contained in the coating composition are hydrolyzed in the presence of water, it is desirable to, before forming the coating composition into a paint, add thereto a water coupler for trapping water contained in the antifouling agent and the pigment. As the water coupler, there are mentioned triethyl orthoformate, tetraethyl silicate ((C2H5O—)4Si), etc. (In the corresponding Japanese Patent No. 2775862, the water coupler is described as an essential component.)
In this coating composition, the source of water is not limited to the antifouling agent and pigment mentioned above, and water is also produced by a reaction between a fatty acid and a pigment, e.g., zinc oxide (ZnO). Thus, in the coating composition described in this reference, water may be produced during the preparation thereof (during the formation into paint). However, a hydrolyzable ester compound or ether compound as the water coupler, after hydrolysis, forms an alcohol. When the polymer has a silyl ester structure, not only is there the possibility of formation of a polycarboxylic acid through transesterification but also dehydration condensation with a silanol produced as a by-product by hydrolysis occurs to thereby form an alkoxysilyl compound, so that the possibility of new water formation is high. Therefore, there is such a problem that the storage stability of the coating composition is poor, and that the coating film obtained therefrom is poor in long-term antifouling properties.
Japanese Patent Laid-open Publication No. 6(1994)-340511 (reference (i)) discloses a marine organism antifouling agent containing a metal salt of organic acid whose solubility in water falls within a specified range. As the organic acid, there is mentioned a saturated aliphatic monocarboxylic acid having 7 to 10 carbon atoms. As the metal for constituting the metal salt of organic acid, there are mentioned metals belonging to Groups Ib, IIa, IIb, IIIa, IIIb, IVa, IVb, Va, Vb, VIa, VIb, VIIa and VIII of the periodic table, such as Cu, Zn and Ni.
Further, it is described that in the use of the marine organism antifouling agent, the antifouling agent can be dissolved in a vehicle, such as an oil based varnish or a chlorinated rubber based resin varnish, before the use.
However, in this reference, there is no description teaching or suggesting a mode wherein a silyl ester copolymer containing constituent units derived from a polymerizable unsaturated carboxylic acid silyl ester is employed as a coating film forming component. Actually, even if only this metal salt (marine organism antifouling agent) is added to a silyl ester copolymer, the obtained antifouling coating composition poses a problem of poor storage stability.
Japanese Patent Laid-open Publication No. 7(1995)-18216 (reference (j)) discloses a coating composition comprising as principal components a polymer (A) from an organosilicon-containing monomer A having in its molecule a triorganosilicon ester group represented by the formula —COO—SiR1R2R3 (I) (wherein each of R1, R2 and R3 is, for example, an alkyl group having 1 to 18 carbon atoms) and copper or a copper compound (B), which coating composition contains as an essential component other than the components (A) and (B) a silicon compound having an alkoxy group represented by the formula: 
(wherein each of R4 to R6 represents, for example, a hydrogen atom, or an alkoxy group or cycloalkoxy group having 1 to 18 carbon atoms; R7 represents, for example, an alkyl group having 1 to 18 carbon atoms; and n is an integer of 1 to 3). In this reference, it is described that a copolymer AB from the above monomer A having the group represented by the formula (I) and a vinyl monomer copolymerizable therewith B may be contained in the coating composition. As the monomer B, there are mentioned (meth)acrylic esters such as methyl (meth)acrylate, ethyl (meth)acrylate and dimethylaminoethyl (meth)acrylate. As the above copper or copper compound (B), there are mentioned copper powder, copper naphthenate, etc. As the above silicon compound having an alkoxy group (C), there are mentioned tetraethoxysilane, tetra-n-butoxysilane and the like. Furthermore, it is described that a pigment such as zinc oxide, a resin such as rosin, etc. may be contained in the coating composition.
However, this silicon compound having an alkoxy group (C), when water is present in the paint, induces a hydrolytic reaction with the water to thereby become an alcohol. Thus, an adverse influence on an increase of water in the paint and coating film is apprehended. Moreover, the silanol after the hydrolysis poses such a problem that silanol molecules undergo a condensation reaction to thereby reproduce water.
In this reference, there is no particular description teaching or suggesting an antifouling coating composition wherein a silyl ester copolymer, a carboxylic acid, a bivalent or trivalent metal compound and a dehydrating agent are employed in combination. The coating film obtained from the coating composition as particularly described in this reference has a drawback in that it is inferior in cracking resistance and antifouling properties, especially, antifouling properties in stationary environment or highly fouling environment.
Japanese Patent Laid-open Publication No. 7(1995)-102193 (reference (k)) discloses a coating composition comprising as essential components an antifouling agent and a copolymer obtained from a monomer mixture containing monomer A represented by the formula X—SiR1R2R3 (wherein R1, R2 and R3 all represent a group selected from among alkyl and aryl groups and may be identical with or different from each other, and X represents an acryloyloxy, a methacryloyloxy, a maleinoyloxy or a fumaroyloxy group), and monomer B represented by the formula Y—(CH2CH2O)n-R4 (wherein R4 represents an alkyl or an aryl group, Y represents an acryloyloxy or a methacryloyloxy group, and n is an integer of 1 to 25). As the antifouling agent, there are mentioned in organic compounds such as cuprous oxide, copper powder and other copper compounds, zinc sulfate and zinc oxide, and further mentioned organometallic compounds such as oxine copper and other organocopper compounds, organonickel compounds, and zinc pyrithione and other organozinc compounds. However, the paint described in this reference has a drawback in that it is inferior in antifouling properties, especially, antifouling properties in stationary environment or highly fouling environment.
Japanese Patent Laid-open Publication No. 8(1996)-199095 (reference (1)) discloses a coating composition comprising as essential components an antifouling agent and a copolymer obtained from a monomer mixture containing the above monomer A represented by the formula X—SiR1R2R3 (1) described in Japanese Patent Laid-open Publication No. 7(1995)-102193 and monomer B represented by the formula Y—(CH(R4))—(OR5) (2) (wherein R4 represents an alkyl group; R5 represents an alkyl or a cycloalkyl group; and Y represents an acryloyloxy, a methacryloyloxy, a maleinoyloxy or a fumaroyloxy group), optionally together with a vinyl monomer C copolymerizable with the monomers A and B. As the vinyl monomer C, there are mentioned, for example, acrylic esters, methacrylic esters, styrene and vinyl acetate. Moreover, as the antifouling agent, there are mentioned inorganic compounds such as cuprous oxide, copper powder and other copper compounds, zinc sulfate and zinc oxide, and further mentioned organometallic compounds such as oxine copper and other organocopper compounds, organonickel compounds, and zinc pyrithione and other organozinc compounds.
Japanese Patent Laid-open Publication No. 8(1996)-269388 (reference (m)) discloses a coating composition comprising, as essential components, bis(2-pyridinethiol-1-oxide) copper salt (copper pyrithione) and a copolymer obtained from a monomer mixture containing monomer A represented by the formula X—SiR1R2R3 (1) (wherein R1, R2 and R3 all represent a hydrocarbon group having 1 to 20 carbon atoms and may be identical with or different from each other, and X represents an acryloyloxy, a methacryloyloxy, a maleinoyloxy, a fumaroyloxy or an it aconoyloxy group), and monomer B represented by the formula Y—(CH2CH2O)n-R4 (2) (wherein R4 represents an alkyl or an aryl group; Y represents an acryloyloxy, a methacryloyloxy, a maleinoyloxy, a fumaroyloxy or an it aconoyloxy group; and n is an integer of 1 to 25). For example, dimethyl-t-butylsilyl acrylate is mentioned as the monomer A. As the antifouling agent, there are mentioned inorganic compounds such as cuprous oxide, copper powder and other copper compounds, zinc sulfate and zinc oxide, and further mentioned organometallic compounds such as oxine copper and other organocopper compounds, organonickel compounds, and zinc pyrithione and other organozinc compounds. Furthermore, for example, rosin and rosin derivatives are mentioned as an elution rate regulator which can be added to the coating composition. However, with respect to the coating film from the paint described in this reference, the antifouling properties in stationary environment are not satisfactory, and there is room for further improvement to, for example, the storage stability of paint.
Japanese Patent Laid-open Publication No. 8(1996)-269389 (reference (n)) discloses a coating composition comprising an antifouling agent and a copolymer from a monomer mixture containing an unsaturated monomer A having a triorganosilyl group and a monomer B represented by any of the following formulae (2) to (9).
The monomer B can be:
monomer having a tertiary amino group, represented by the formula CH2═CR4COOR5—NR6R7 (2) (wherein R4 represents H or CH3; R5 represents an alkylene group; and R6 and R7 represent alkyl groups and maybe identical with or different from each other),
monomer containing a quaternary ammonium salt, represented by the formula CH2═CR8COOR9—NR10R11R12(Y) (3) (wherein R8 represents H or CH3; R9 represents an alkylene group; R10 to R12 represent alkyl groups and maybe identical with or different from each other; and Y represents a halogen atom),
monomer containing a nitrogen-containing heterocycle, represented by the formula CH2═CH—Z (4) (wherein Z represents a group comprising a nitrogen-containing heterocycle),
monomer having in its molecule an alkoxy group or an aryloxyalkylene glycol group, represented by the formula CH2═CR13COO(R14O)m(R15O)n(R16O)o-R17 (5) (wherein R13 represents H or CH3; R14 represents an ethylene group; R15 represents an alkylene group having 3 carbon atoms; R16 represents an alkylene group having 4 carbon atoms; R17 represents an alkyl group or aryl group; and each of m, n and o is an integer of 0 or greater, provided that n and o are not simultaneously 0),
(meth)acrylamide represented by the formula CH2═CR18CONR19R20 (6) (wherein R18 represents H or CH3; and R19 and R20 represent alkyl groups and may be identical with or different from each other),
(meth)acrylamide having a nitrogen-containing cyclic hydrocarbon group, represented by the formula CH2═CR21CON( )Q (7) (wherein R21 represents H or CH3; and N( )Q is a nitrogen-containing group wherein, for example, O, N or S may be contained in Q),
(meth)acrylic ester containing a furan ring, represented by the formula CH2═CR23COOCH2—T (8) (wherein R23 represents H or CH3; and T represents a furan ring or a tetrahydrofuran ring), or
monomer of the formula CH2═CH—CN (9).
Further, as an optional component copolymerizable with the above monomers A and B, there are mentioned various copolymerizable monomers such as acrylic acid, ethyl acrylate, 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate.
In the Example portion of the reference, there are mentioned, for example, a copolymer from tri-n-butylsilyl acrylate (TBSA), diethylaminoethyl methacrylate (DEAEMA) and methyl methacrylate (MMA), and a copolymer from tri-n-butylsilyl acrylate (TBSA), N,N-dimethylacrylamide (DMAA) and methyl methacrylate (MMA).
Still further, as a component which can be added to the coating composition, there are mentioned the same antifouling agents as described in the above Japanese Patent Laid-open Publication No. 8(1996)-269388.
Japanese Patent Laid-open Publication No. 8(1996)-269390 (reference (o)) discloses a coating composition comprising:
a polymer from monomer A represented by the formula X—SiR1R2R3 (1) (wherein R1, R2 and R3 all represent groups selected from among alkyl and aryl groups and may be identical with or different from each other, and X represents an acryloyloxy, a methacryloyloxy, a maleinoyloxy, a fumaroyloxy or an itaconoyloxy group),
a polymer from monomer B represented by the formula Y—(CH2CH2O)n-R4 (2) (wherein R4 represents an alkyl or an aryl group; Y represents an acryloyloxy, a methacryloyloxy, a maleinoyloxy, a fumaroyloxy or an itaconoyloxy group; and n is an integer of 1 to 25), and
an antifouling agent. As the antifouling agent, there are mentioned the same antifouling agents as described in the above Japanese Patent Laid-open Publication No. 8(1996)-269388. Further, as a component which can be added to the coating composition, there are mentioned, for example, resins such as rosin and antisetting agents. However, with respect to the coating film from the coating composition described in this reference, there is room for further improvement to the antifouling properties in stationary environment, and there is room for improvement to the storage stability of paint.
Japanese Patent Laid-open Publication No. 8(1996)-277372 (reference (p)) discloses a coating composition comprising a triphenylboron pyridine complex and a copolymer from a monomer mixture containing the monomer A represented by the formula X—SiR1R2R3 (1) described in the above Japanese Patent Laid-open Publication No. 8 (1996)-269388 (reference (m)) and the monomer B represented by the formula Y—(CH2CH2O)n-R4 (2) described in the same reference, wherein the resin component and marine organism adhesion inhibitor consist only of a nonmetallic polymer and an on metallic organic inhibitor, respectively. Further, for example, rosin and rosin derivatives are mentioned as an elution rate regulator which can be added to the coating composition. However, with respect to the coating film from the coating composition described in this reference, the antifouling properties in stationary environment are not satisfactory, and there is room for improvement to the storage stability of paint.
Japanese Patent Laid-open Publication No. 10(1998)-30071 (reference (q)) discloses a coating composition comprising at least one rosin compound (A) consisting of rosin, a rosin derivative or a rosin metal salt; a polymer having an organosilyl ester group (B) consisting of a polymer from at least one monomer M represented by the formula X—SiR1R2R3 (1) (wherein R1 to R3 all represent groups selected from among alkyl and aryl groups and may be identical with or different from each other, and X represents an acryloyloxy, a methacryloyloxy, a maleinoyloxy, a fumaroyloxy, an itaconoyloxy or a citraconoyloxy group), and/or a polymer from the above at least one monomer M and at least one other polymerizable monomer; and an antifouling agent (C). As the antifouling agent, there are mentioned a wide variety of organic and inorganic antifouling agents, such as zinc oxide and copper naphthenate, which are the same as described in the above Japanese Patent Laid-open Publication No. 8(1996)-269388. Further, as components which can be added to the coating composition, there are mentioned, for example, pigments, water couplers, chlorinated paraffin and antisetting agents.
However, with respect to the paints and coating films disclosed in these references (k) to (q), the paints exhibit unsatisfactory storage stability, and the coating films are unsatisfactory in a balance of cracking resistance, peeling resistance (adherence of coating film), antifouling performance, in particular, antifouling properties in stationary environment, long-term antifouling properties and self-polishing properties.
Further, for example, 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate are mentioned as a copolymerizable optional component in Japanese Patent Publication No. 5(1993)-82865 (reference (r)). Still further, silyl (meth)acrylate copolymers are described in Japanese Patent Laid-open Publication No. 9(1997)-48947 (reference (s)), Japanese Patent Laid-open Publication No. 9(1997)-48948 (reference (t)), Japanese Patent Laid-open Publication No. 9(1997)-48949 (reference (u)), Japanese Patent Laid-open Publication No. 9(1997)-48950 (reference (v)), Japanese Patent Laid-open Publication No. 9(1997)-48951 (reference (w)), Japanese Patent Publication No. 5(1993)-32433 (reference (x)), U.S. Pat. No. 4,593,055 (reference (y)), Japanese Patent Laid-open Publication No. 2(1990)-196869 (reference (z)) and WO 91/14743 (reference (za)) However, with respect to the antifouling paints from the copolymers described in these references (r) to (za), there is room for further improvement to the storage stability thereof, and to, regarding the coating films therefrom, the balance of cracking resistance, peeling resistance (adherence of coating film), antifouling performance, in particular, antifouling properties in stationary environment and highly fouling environment, long-term antifouling properties and self-polishing properties.
Japanese Patent Laid-open Publication No. 63(1988)-215780 (reference (zb)) describes copolymers formed using, for example, methyl methacrylate, n-butyl methacrylate and acrylamide as copolymerization components, and further describes antifouling paints containing the above copolymers and cuprous oxide. However, these antifouling paints have the same drawbacks as those of the antifouling paints of the above references.
Japanese Patent Laid-open Publication No. 11(1999)-335619 (reference (zc)) discloses an antifouling coating composition comprising a copolymer from a monomer having a triorganosilyl group, represented by the formula (1) given below, and another ethylenically unsaturated monomer which is copolymerizable with the above monomer; a carboxyl group-containing monobasic acid; and a metal-containing antifbuling agent. 
wherein R1 represents H or CH3; and each of R2, R3 and R4 independently represents a group selected from the group consisting of an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group and an aryl group.
Japanese Patent Laid-open Publication No. 11(1999)-343451 (reference (zd)) discloses an antifouling coating composition comprising a copolymer from a monomer having a triorganosilyl group, represented by the formula (2) given below, and another ethylenically unsaturated monomer which is copolymerizable with the above monomer; a carboxyl group-containing monobasic acid; and a metal-containing antifouling agent. 
wherein each of R1, R2 and R3 independently represents a group selected from the group consisting of an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group and an aryl group.
Japanese Patent Laid-open Publication No. 2000-63737 (reference (ze)) discloses an antifouling coating composition comprising a copolymer from a monomer having a triorganosilyl group, represented by the above formula (1), and another ethylenically unsaturated monomer which is copolymerizable with the above monomer; a metallic soap of carboxyl group-containing monobasic acid; and a metal-containing antifouling agent.
However, with respect to the antifouling coating compositions described in these references (zc) to (ze), the storage stability thereof is not satisfactory, and lowering of the paint viscosity is so difficult that the use of much solvent has been inevitable. In particular, recently, there has been the problem that although it is demanded to reduce the amount of solvent added to a coating composition taking environmental pollution into account, it is difficult to prepare a paint of low solvent content from the antifouling coating compositions described in the references (zc) to (ze).